A conventional button key can be classified into two types.
That is, in a film insert type, a character part and a backlighting part are printed on a thin plastic film, and the printed film is formed into a button shape and then inserted into an injection mold, and a button is injection-molded using a transparent plastic material and then assembled separately with a key pad rubber. In a mold type, a button is injection-molded by using a transparent plastic material, and the molded button is colored in a spraying way, and only a character part becomes transparent for backlighting in a laser marking way, and the button is UV-coated in order to secure wear resistance and then boned to a key pad rubber.
However, in the film insert type, the film part may be separated upon being used for a long period of time, and the film may be separated from the injection-molded part during a thermal shock test. In particular, it is not possible to provide the luxurious texture.
Further, in the mold type, the wear resistance is deteriorated, and since it is not possible to provide the metallic texture, there is limitation in providing the luxurious texture.
In order to the above-mentioned problems, the button key is recently formed of a metallic material as described in Korean Patent Laid-Open No. 10-2005-0047275.
FIG. 8 shows a process of manufacturing a conventional button key.
A button-shaped case 10 shown in FIG. 8b is formed by various methods such as pressing or die-casting by using a metal sheet S having a desired thickness, as shown in FIG. 8a, and a space 13 is formed in the case 10.
Then, as shown in FIG. 8c, a cutting process is performed on a surface of the case 10 corresponding to a character or a number, thereby forming a display hole 11.
If the cutting process of the display hole 11 is finished, the molded case 10 is inserted into a mold, and then a transparent liquid thermoplastic resin is put into the space 13 of the case 10, and thus a filling part 20 formed of a transparent plastic material is provided at the space 13 and display hole 11.
In the manufacturing process of the conventional button key, the display hole 11 having a corresponding shape to the number or character is formed first, and the plastic filling part 20 is formed.
Therefore, in case of a portion, such as an “O” shape, that is formed into a closed curve so that inside and outside parts thereof are separated from each other, since the inside part may be moved or separated during the cutting process, it is difficult to precisely form the shape, and thus it is necessary to separately form a supporting portion for connecting the inside and outside parts.